Field of the Invention
The present invention relates to improved polymer-derived ceramic composites and methods of making and using the same.
Description of Related Art
Powering of electric vehicles or next generation wearable electronic devices that run on Li-ion battery (LIB) technology will require new electrode materials beyond the traditional graphite anode because of its poor rate capability and low charge capacity (theoretical charge capacity approx. 372 mAh·g−1), which has already been realized. Therefore, desired characteristics of an advanced LIB system are high power and energy density, safety, long-life, and lightweight. Recent research has shown that Si anodes can drastically increase the capacity of existing LIB by more than 30%. However, Si suffers from huge volume changes during charge/discharge cycles and has poor electrical conductivity that generally leads to poor rate capability.
Polymer-derived ceramics, such as silicon carbide (SiC), siliconoxycarbide (SiOC), silicon carbonitride (SiCN), aluminum nitride (AlN), and hafnium carbide (HfC), can be synthesized by thermal decomposition of suitable polymeric precursors, and possess some remarkable properties, such as high oxidation resistance, high temperature piezoresistivity, high mechanical strength, and photoluminescence. One advantage of polymer-derived ceramics is that their microstructure can be modified on a molecular scale through modification of the polymer precursor. Most silicon-based polymer-derived ceramics are amorphous ceramics, prepared by controlled heating of polysilazane- or polysiloxane-based liquid polymeric precursors. The final ceramic's chemical and physical properties are known to depend on the initial molecular arrangement of the polymeric precursor and processing conditions. Numerous engineered Si nanomaterial like nanowires, nanoparticles and hollow nanospheres have shown promising results in laboratory experiments, however, a practical and cost-effective solution is yet to be realized.